Vertical Hall devices may be used to sense or measure physical quantities. In order to sense or measure the strength and/or the direction of a magnetic field parallel to the surface of, e.g., a semiconductor die, vertical Hall devices may be used. Most vertical Hall devices suffer from the fact that the spinning current method, which is used to cancel the zero-point error of the vertical Hall device, does not work very well. With known methods of the spinning current scheme it is possible to obtain residual point errors of about 1 mT. A reason for this rather poor offset behavior can be found in the asymmetry of the vertical Hall device. This residual zero-point error of vertical Hall sensors which respond to magnetic field components parallel to the substrate is common to most vertical Hall devices. The zero-point error is also referred to as offset error.
The offset error (or offset) is the output signal in the absence of the magnetic field which the sensor should detect. The origin of the offset error is basically an asymmetry of the device. This asymmetry can be caused by asymmetry in the geometrical shape (which of course one tries to avoid). Yet, even in the case of near-perfect geometrical asymmetry, the potential distribution in the device causes an asymmetry, due to the junction-field-effect. The junction-field-effect owes its name from an analogy to the working principle of the junction-field-effect transistor (JFET). According to this technique, an active volume within the substrate is confined by a reverse biased pn-junction forming an isolating depletion layer. However, the thickness of this layer is voltage dependent. During operation, Hall voltage and magneto-resistance effect lead to potential variation inside the device and the active volume is deformed causing some kind of junction-field-effect non-linearity.